Air handling duct systems are routinely fitted with air quality detectors such as smoke detectors or carbon monoxide detectors so as to detect an air quality problem and the resulting hazard before the gas is further distributed by the air handling system. Such detectors are routinely placed within a housing receiving inlet sample gas from an air handling system conduit and an outlet exhaust from which air handling system gas is returned to the same or different conduit of the air handling system so as to create a swirling flow pressure differential of air handling system gas around the detector within the housing. Such detectors are periodically tested to assure that a detector properly samples and signals an alarm in response to exposure to a target level of gas or activation of a test circuit.
A conventional air handling duct detector housing has a number of limitations that complicate testing and assured operation of a detector contained therein. A representative prior art air handling duct detector housing is provided in FIG. 1. A conventional housing has a body including midline inlet I and outlet O apertures along line M-M′ for air to pass therethrough and a cover C that is often transparent that secures to the housing body by way of threaded fasteners F. The housing volume is proportioned and divided to accommodate a given detector D and related printed circuit boards P and electronics needed for coupling to a relay board, providing various normal, alarm, and trouble output signals and the like. The configuration of the air inlet and outlet apertures in communication with an air duct are routinely positioned midline within the housing as shown in FIG. 1. When moisture-laden air is conveyed through the air handling system, or alternatively the housing is at a lower temperature than the inlet air, condensation tends to collect within the housing. Under prolonged condensation conditions, water can accumulate in the housing to the midline of the housing resulting in active detector elements for electronic components being submerged in water resulting in emergency service to avoid component failure. Additionally, the seal line at the interface between the housing body and cover, while providing a generally waterproof seal, provides an inadequate barrier against vapor and the thermocycling associated with outdoor placement and as such a detector housing of FIG. 1 is limited to indoor placement. Still another limitation found in a conventional prior art housing is reliance on multiple threaded fasteners to provide a gradual tightening of the cover to the housing body. As a result a loose cover placement will not signal a warning and inhibit proper operation of a detector system. The simultaneous operation of a screwdriver to drive threaded fasteners while holding already removed fasteners, stabilizing the cover all while often balancing on a ladder also leads to inefficient servicing, unpredictable alarm operation and a falling hazard.
In view of the limitations found in a conventional prior art housing, there exists a need for an air handling system duct detector housing that is less vulnerable to detector failure through water egress and provides assured repeatability of sealing. There also exists a need for a detector housing that expedites detector testing and servicing and assures proper alarm operation.